Speed Control of a DC Motor

Paper No: 349b

Web-based Unit Operations and Process Control Experiments

Jim Henry (speaker),

University of Tennessee at Chattanooga,

TN 37377

Eric Nuttall, Lomesh Dutta and Nader Vadiee

University of New Mexico,

Albuquerque, NM 87122

Keywords: Virtual laboratory, process control, MIMO systems, nonlinear control

Prepared for presentation at the Session 349 of Annual AICHE conference,

Nov 16-21, 2003

Copyright © 2003 Jim Henry, University of Tennessee at Chattanooga

Eric Nuttall, Lomesh Dutta and Nader Vadiee, University of New Mexico

AIChE shall not be responsible for statements or opinions contained in papers or printed in its publications
Abstract:

What did we adopt from the Summer School? This paper describes the collaboration established between the University New Mexico (UNM) and the University of Tennessee (UTC) at Chattanooga for the development of internet operated chemical engineering labs. The close working collaboration developed directly from contacts made at the Summer School. This paper describes how our School of Engineering has developed an interdisciplinary web-based process control laboratory called the Coordinated Systems and Control Laboratory. The CSC Laboratory provides lecture demonstrations for undergraduate systems and control courses offered at EECE, ME and CHNE engineering school departments. This lab also offers design and development projects for advanced undergraduate students in those departments. The CSC laboratory helps students familiarize themselves with such software as MATLAB, MATHEMATICA, CONTROL STATION, SIMULINK, and LabVIEW. The CSC Laboratory’s 8 Stations include:
* Rotary Pendulum system – Position Control

* Speed control of a DC motor
* Translational Inverted Pendulum System
* Three Tank System
* Magnetic Levitation System
* Rhino Robot Module
* LabVIEW Set-up

Introduction

What did we adopt from the Summer School?

Laboratories are historically a key part of the chemical engineering curriculum but present many challenges to fund, maintain and upgrade. I along with many Summer School faculty attended the sessions on innovative laboratories and toured the modern laboratory facilities at the University of Colorado. It was at the innovative laboratories sessions that I was first introduced to web based experiments and Professor Jim Henry who is a leader in this technology and was presenting his work on web based laboratory experiments. From Prof. Henry’s presentations, I was convinced that this approach was a true advancement in how we operate laboratory experiments and students gain a laboratory experience. The ability of student to access, operate, and control experiments at any location and at any time provides a unique learning opportunity and takes us from the traditional fixed laboratory period to a new level and opportunity in teaching the basic principles provided through the laboratory experience.

Hence the question for me was how to take this new laboratory approach back to the University of New Mexico (UNM) where like many universities funds and resources for new efforts are limited. UNM was fortunate to have a NASA funded project within our School of Engineering The NASA Pursue program was committed to developing integrated laboratories primarily in process control that could be shared by multiple departments. The NASA Pursue program became the home for my development of a three-tank web based process control experiment and during the past year many web based process control experiments have been developed. This was the start of extensive collaborations with Prof. Jim Henry.

This paper describes how the NASA purse program provided a basis for developing web base experiments and details on the three-tank web based process control experiment which was developed as a collaborative effort between the University of New Mexico (Eric Nuttall) and the University of Tennessee (UTC) (Jim Henry)

Description of the NASA Pursue Program and the Web Based Laboratory

PURSUE is a program funded by NASA at the University of New Mexico (UNM) and its collaborating higher education institutions, to build upon their funded research to augment the quality undergraduate education in the fields of Mathematics, Science, Engineering and Technology (MSET) .The program aims at strengthening the hands on research experience for undergraduates and high school students in these fields and integrate the cutting-edge science and technology concepts into undergraduate curriculum , as well as introductory-level courses and laboratories for majors and non-majors.

PURSUE engages all five School of Engineering Departments: Chemical and Nuclear Engineering, Civil Engineering, Computer Science, Electrical and Computer Engineering, and Mechanical Engineering. Also the program has participation from the departments of Biology, Chemistry, Earth and Planetary Sciences (with the Institute of Meteoritics), Mathematics and Physics and Astronomy. The program has involved more than 300 students, who have gained research experience in a multitude of projects. PURUSE also hosts summer programs for high school students selected by NASA from all over the country where they find an opportunity to be involved in research related activities.

The Coordinated Systems and Control Laboratory (CSC) has been developed as an innovative shared effort between the NASA PURSUE program at UNM, its affiliated schools and the University of Tennessee at Chattanooga (UTC) to capitalize on the synergism resulting from our similar interests. The approach demonstrates an opportunity to share infrastructure and experimentation strategies amongst schools and thus being able to enhance communication and collaborative research connecting them.

The CSC laboratory is an interdisciplinary web based process control laboratory that provides lecture demonstrations for undergraduate systems and control courses offered at EECE, ME and CHNE engineering school departments. This lab also offers design and development projects for advanced undergraduate students in those departments. The CSC laboratory helps students familiarize themselves with such software as MATLAB, MATHEMATICA, CONTROL STATION, SIMULINK, WINCON and LabVIEW.

The CSC includes the following experiments which are related to department outside of chemical engineering but may in the future be of interest to chemical engineers.

Rotary Pendulum System-Position Control:

This experiment serves as an educational and research tool for a multitude of engineering fields. On one hand where some simple experiments could be used to demonstrate important concepts of engineering dynamics and the application of control systems in engineering design, on the other hand several advanced experiments which cater the curriculum in frequency domain and state space control system analysis, real time programming, linear and nonlinear control and intelligent control could be developed. The apparatus is interfaced to the computer using WINCONTM real time. The system is fully compatible with MATLABä, Simulink and Real-Time workshop. Currently, the web based control capabilities of the system are being examined at both UNM and UTC.

Speed control of a DC motor:

The apparatus for this system consists of a Canon CKT26-T5 motor with tachometer, and is driven by an Apex PA26 high power op-amp. This experiment is designed to help students of EECE and ME get familiar with a variety of DC motor applications including conveyor belts, robotics, etc., where it is important to maintain a constant speed under load variations. The experiment provides user the ability to design control algorithms and compare their results with MATLABä simulations over the web.

Linear Inverted Pendulum:

The experiment is intended for students in Electrical Engineering to design and test their control algorithms and attempt to stabilize an inverted pendulum mounted on a motor driven cart. This system stands as a classical model of a nonlinear and unstable plant. Discrete time and fuzzy logic controllers for this system were designed in LabVIEW that allow the students to input the parameters calculated by them and test the stability of their own controller. The simulations were performed in MATLAB

Magnetic Levitation system:

The purpose of the experiment is to provide students a platform to design their controllers that could levitate the ball from the post and to track the ball position to a desired trajectory. The posts also provide repeatable initial conditions for control system performance evaluation. The apparatus was interfaced via the MultiQ- PCI DAQ board and is controlled by WINCONTM real time software supplied by quansar, the manufacturer of the system.

Rhino Robot:

The Rhino Robot provides a means for engineering students to develop controller systems capable of directing each movement of the arm and thus use the robot in their respective tailored applications . The system serves the curriculum targets each of CHNE, EECE and ME departments. Currently, several improvements in the robot function including pressure sensing devices on the robot’s fingers for precision controls, and visual sensing devices to distinguish between different objects for complex instructions are being tested. The ability to control the robot over the internet is also being examined.

LabVIEW station:

Provides freshmen level undergraduate students an ability to familiarize themselves with LabVIEW using instrument simulator cards.

Currently the status of the CSC is:

·  The laboratory is still being development. Though the three-tank system development, testing and implementation is complete. Development and testing required about one year.

·  The NASA funding for this program is in final stage.

·  The costs for hardware and software maintenance are hardware and software is high.

The lab also requires at least two assigned Teaching Assistants to manage the lab equipments and online facilities.

Description of the Three-Tank Process Control Experiment

The control of non linear systems, particularly multi-variable systems, plays a very significant part in the advancement of automation of technical processes. One of the classic examples of such systems is a “Three Tank System” as illustrated in Figure 1. This experiment presents an excellent test bed for nonlinear system decoupling and control.

The basic apparatus consists of three interconnected plexi-glass tanks numbered from left to right as tank 1, tank 3 and tank 2. All three tanks are connected with the third tank in series, tank 2, which drains to the system exit. Liquid is pumped into the first and the third tanks to maintain their levels. The level in the middle tank affects the level in the two end tanks. Each tank is fitted with a static pressure sensor, which gives a voltage output proportional to the level of liquid in the tank.

.

Figure 1 Schematic diagram of the three tank system

There are six manual valves v1, v2...v6 that can be used to vary the configuration of the process or to introduce disturbances or faults. Two variable speed pumps driven by DC motor are used in this apparatus. These pumps are designed to give an accurate well defined flow per rotation. Thus, the flow rate provided by each pump is proportional to the voltage applied to its DC motor. Q1 and Q 2 are the flow rates of liquid into tank1 and tank2. The apparatus is interfaced to a computer using the National Instruments, DAQ 6024-E data acquisition card. This DAQ card allows for sampling of 16 separate differential analog inputs and provides with 2 analog outputs. With this setup it is possible to control the apparatus via any computer on the internet thus enabling students to have round the clock access to the experiment.

This experiment serves as an excellent test bed for non linear multivariable process control problems. The control of liquid levels in such systems is particularly common in chemical process industries. The experimental procedures are designed according to the curriculums of the Chemical, Mechanical and Electrical engineering as the apparatus provides the capability of level control, nonlinear system decoupling and designing of control algorithms and thus holds special interests to each of these fields. The basic apparatus consists of three interconnected plexi-glass tanks connected in series. Two variable speed diaphragm pumps capable of providing an accurate well defined flow per rotation are used to feed the two tanks on the either side. The middle tank helps in controlling their levels to the desired set point as specified by the user. Each tank is fitted with a static pressure sensor, which gives a voltage output proportional to the level of liquid in the tank. Each tank is fitted with a static pressure sensor, which gives a voltage output proportional to the level of liquid in the tank. The students in LabVIEWTM environment performed the data acquisition and the implementation of a PI controller as illustrated in Fig. 2 showing the web based controller window. The experiment also allows the user to compare the results obtained with the simulation program developed in SimulinkTM and MathematicaTM.

Figure 2: Three tank system in PI control mode on the web

Summary

The Summer School provided an opportunity to learn about a new approach to laboratories and collaboration with a colleague that had many years of experience in this area. Several web based process control experiments have subsequently been developed and are being integrated into the undergraduate curriculum. We are still learning how to introduce students to these experiments and maximize their educational benefits.

Challenges of continued funding and staffing of the Coordinated Systems and Control Laboratory are being addressed through the Dean of Engineering and the Department Chairs.

References

1. Franklin, G.F., J.D. Powell, and A. Emami-Naeini, Feedback Control of Dynamic Systems, 4th ed., NJ: Prentice-Hall, 2002.

2. Phillips .L., and R.D. Harbor, Feedback Control Systems, 2nd ed., NJ: Prentice-Hall,

1991.

3. Three-Tank System, DTS200 Practical Instructions, 1996

4. PI Control of the "Three tank System" Alireza Naddaf, Lomesh Dutta, (submitted to IEEE, Summer, 2003)

5. PI control of "Three tank System" -- Alireza Naddaf, Lomesh Dutta et al report submitted to NASA pursue, April 2003

Acknowledgements

We wish to thank the organizers, sponsors and hosts of the ASEE Chemical Engineering Summer School 2002.

UNM work in the Coordinated Systems and Control Laboratory has been supported in part under the PURSUE Project at UNM with grants from NASA.

UTC's Center of Excellence for Computer Applications has supported this effort with a generous grant. Other support has been received from the UTC College of Engineering and Computer Science and National Instruments. Partial support for this work in the lab is being provided by the National Science Foundation's Division of Undergraduate Education, Instructional Laboratory Improvement (ILI) grant DUE #97-51024.

Biographical Information

ERIC NUTTALL

Eric Nuttall is Professor of Chemical and Nuclear Engineering at the University of New Mexico. He directs